This document provides information on potentiometry and potentiometric titration. It discusses the basic principles of potentiometry including electrode potentials and how a potential difference is established between an electrode and solution. It describes the instrumentation used including reference electrodes like calomel and silver-silver chloride electrodes and indicator electrodes like metal, glass membrane, and quinhydrone electrodes. It also discusses different types of potentiometric titrations and provides examples of applications for potentiometry in various industries.
ESTIMATION OF THE RATE OF REACTION WILL BE DONE BASED ON THE POTENTIAL DIFFERENCE BETWEEN REFERENCE AND INDICATOR ELECTRODE. THE POTENTIAL OF THE REFERENCE ELECTRODE IS STABLE WHERE AS THE POTENTIAL OF THE INDICATOR ELECTRODE VARIES WITH THE POTENTIAL OF THE SOLUTION IN WHICH IT IS PLACED
Polarographic technique is applied for the qualitative or quantitative analysis of electroreducible or oxidisable elements or groups.
It is an electromechanical technique of analyzing solutions that measures the current flowing between two electrodes in the solution as well as the gradually increasing applied voltage to determine respectively the concentration of a solute and its nature.
The principle in polarography is that a gradually increasing negative potential (voltage) is applied between a polarisable and non-polarisable electrode and the corresponding current is recorded.
Polarisable electrode: Dropping Mercury electrode
Non-polarisable electrode: Saturated Calomel electrode
From the current-voltage curve (Sigmoid shape), qualitative and quantitative analysis can be performed. This technique is called as polarography, the instrument used is called as polarograph and the current-voltage curve recorded is called as polarogram
Amperometry refers to the measurement of current under a constant applied voltage and under these conditions it is the concentration of analyte which determine the magnitude of current.
In Amperometric titrations, the potential applied between the indicator electrode (dropping mercury electrode) and the appropriate depolarizing reference electrode (saturated calomel electrode) is kept constant and current through the electrolytic cell is then measured on the addition of each increment of titrating solution. It is a form of quantitative analysis.
Otherwise called as Polarographic or polarometric titrations.
ESTIMATION OF THE RATE OF REACTION WILL BE DONE BASED ON THE POTENTIAL DIFFERENCE BETWEEN REFERENCE AND INDICATOR ELECTRODE. THE POTENTIAL OF THE REFERENCE ELECTRODE IS STABLE WHERE AS THE POTENTIAL OF THE INDICATOR ELECTRODE VARIES WITH THE POTENTIAL OF THE SOLUTION IN WHICH IT IS PLACED
Polarographic technique is applied for the qualitative or quantitative analysis of electroreducible or oxidisable elements or groups.
It is an electromechanical technique of analyzing solutions that measures the current flowing between two electrodes in the solution as well as the gradually increasing applied voltage to determine respectively the concentration of a solute and its nature.
The principle in polarography is that a gradually increasing negative potential (voltage) is applied between a polarisable and non-polarisable electrode and the corresponding current is recorded.
Polarisable electrode: Dropping Mercury electrode
Non-polarisable electrode: Saturated Calomel electrode
From the current-voltage curve (Sigmoid shape), qualitative and quantitative analysis can be performed. This technique is called as polarography, the instrument used is called as polarograph and the current-voltage curve recorded is called as polarogram
Amperometry refers to the measurement of current under a constant applied voltage and under these conditions it is the concentration of analyte which determine the magnitude of current.
In Amperometric titrations, the potential applied between the indicator electrode (dropping mercury electrode) and the appropriate depolarizing reference electrode (saturated calomel electrode) is kept constant and current through the electrolytic cell is then measured on the addition of each increment of titrating solution. It is a form of quantitative analysis.
Otherwise called as Polarographic or polarometric titrations.
It is an electrochemical method of analysis used for the determination or measurement of the electrical conductance of an electrolyte solution by means of a conductometer.
Electric conductivity of an electrolyte solution depends on :
Type of ions (cations, anions, singly or doubly charged
Concentration of ions
Temperature
Mobility of ions
The main principle involved in this method is that the movement of the ions creates the electrical conductivity. The movement of the ions is mainly depended on the concentration of the ions.
The electric conductance in accordance with ohms law which states that the strength of current (i) passing through conductor is directly proportional to potential difference & inversely to resistance.
i =V/R
The earliest voltammetric technique
Heyrovsky invented the original polarographic method in 1922, conventional direct current polarography (DCP).
It employs a dropping mercury electrode (DME) to continuously renew the electrode surface.
Diffusion is the mechanism of mass transport.
When an external potential is applied to a cell
containing a reducing substance such as CdCl2,
The following reaction will occur:
Cd2+ + 2e + Hg = Cd(Hg)
The technique depends on increasing the applied
voltage at a steady rate and simultaneously
record photographically the current-voltage
curve (polarogram)
The apparatus used is called a polarograph .
When an external potential is applied to a cell
containing a reducing substance such as CdCl2,
The following reaction will occur:
Cd2+ + 2e + Hg = Cd(Hg)
The technique depends on increasing the applied
voltage at a steady rate and simultaneously
record photographically the current-voltage
curve (polarogram)
The apparatus used is called a polarograph .
Capillary tube about 10-15cm
Int. diameter of 0.05mm
A vertical distance being maintained betwwen DME and the solution
Drop time of 1-5 seconds
Drop diameter 0.5mm
The supporting electrolyte
is a solution of (KNO3, NaCl, Na3PO4) in which the sample (which must be electroactive) is dissolved.
Function of the supporting electrolyte
It raises the conductivity of the solution.
It carries the bulk of the current so prevent the
migration of electroactive materials to working
electrode.
It may control pH
It may associate with the electroactive solute as
in the complexing of the metal ions by ligands.
content- Principle
Ilkovic equation
Construction and working of dropping mercury electrode and rotating platinum electrode
Applications
Polarography is a voltammetric technique in which chemical species (ions or molecules) undergo oxidation (lose electrons) or reduction (gain electrons) at the surface of a dropping mercury electrode (DME) at an applied potential. Polarography only applies to the DME.
Objective of polarography
Polarography is an electroanalytical technique that measures the current flowing between two electrodes in the solution (in the presence of gradually increasing applied voltage) to determine the concentration of solute and its nature respectively
Polarography is based upon the principle that gradually increasing voltage is applied between two electrodes, one of which is polarisable (dropping mercury electrode) and other is non-polarisable and current flowing between the two electrodes is recorded.
A sigmoid shape current-voltage curve is obtained from which half wave potential as well as diffusion current is calculated.
Diffusion current is used for determination of concentration of substance.
Half wave potential is characteristic of every element.
Ilkovic equation is a relation used in polarography relating the diffusion current (id) and the concentration of the non-polarisable electrode, i.e., the substance reduced or oxidised at the dropping mercury electrode (polarisable electrode).
Definitions of types of currents
1. Residual current (ir), 2. Migration current (im): , 3. Diffusion current (id) 4.Half wave potential 5. Limiting current (il)
Dropping mercury electrode- Dropping mercury electrode (DME) is a polarisable electrode and can act as both anode and cathode.
The pool of mercury acts as counter electrode,
i.e., anode if DME is cathode or
cathode if DME is anode.
The counter electrode is a non-polarisable electrode.
To the analyte solution, electrolyte like KCl is added i.e., 50-100 times of sample concentration.
Pure nitrogen or hydrogen gas is bubbled through the solution, to expel (remove) out oxygen.
Eg: If the analyte solution contains cadmium ions, then cadmium ions are discharged at cathode (-)
Cd2+ + 2e- → Cd
Then, gradually increasing voltage is applied to the polarographic cell and current is recorded.
Graph is plotted between voltage applied and current. This graph is called Polarograph and the apparatus is known as Polarogram.
The diffusion current produced is directly proportional to concentration of analyte and this is used in quantitative analysis.
The half wave potential is characteristic of every compound and this is used in qualitative analysis.
Graph is plotted between voltage applied and current. This graph is called Polarograph and the apparatus is known as Polarogram.
The diffusion current produced is directly proportional to concentration of analyte and this is used in quantitative analysis.
The half wave potential is characteristic of every compound
It is an electrochemical method of analysis used for the determination or measurement of the electrical conductance of an electrolyte solution by means of a conductometer.
Electric conductivity of an electrolyte solution depends on :
Type of ions (cations, anions, singly or doubly charged
Concentration of ions
Temperature
Mobility of ions
The main principle involved in this method is that the movement of the ions creates the electrical conductivity. The movement of the ions is mainly depended on the concentration of the ions.
The electric conductance in accordance with ohms law which states that the strength of current (i) passing through conductor is directly proportional to potential difference & inversely to resistance.
i =V/R
The earliest voltammetric technique
Heyrovsky invented the original polarographic method in 1922, conventional direct current polarography (DCP).
It employs a dropping mercury electrode (DME) to continuously renew the electrode surface.
Diffusion is the mechanism of mass transport.
When an external potential is applied to a cell
containing a reducing substance such as CdCl2,
The following reaction will occur:
Cd2+ + 2e + Hg = Cd(Hg)
The technique depends on increasing the applied
voltage at a steady rate and simultaneously
record photographically the current-voltage
curve (polarogram)
The apparatus used is called a polarograph .
When an external potential is applied to a cell
containing a reducing substance such as CdCl2,
The following reaction will occur:
Cd2+ + 2e + Hg = Cd(Hg)
The technique depends on increasing the applied
voltage at a steady rate and simultaneously
record photographically the current-voltage
curve (polarogram)
The apparatus used is called a polarograph .
Capillary tube about 10-15cm
Int. diameter of 0.05mm
A vertical distance being maintained betwwen DME and the solution
Drop time of 1-5 seconds
Drop diameter 0.5mm
The supporting electrolyte
is a solution of (KNO3, NaCl, Na3PO4) in which the sample (which must be electroactive) is dissolved.
Function of the supporting electrolyte
It raises the conductivity of the solution.
It carries the bulk of the current so prevent the
migration of electroactive materials to working
electrode.
It may control pH
It may associate with the electroactive solute as
in the complexing of the metal ions by ligands.
content- Principle
Ilkovic equation
Construction and working of dropping mercury electrode and rotating platinum electrode
Applications
Polarography is a voltammetric technique in which chemical species (ions or molecules) undergo oxidation (lose electrons) or reduction (gain electrons) at the surface of a dropping mercury electrode (DME) at an applied potential. Polarography only applies to the DME.
Objective of polarography
Polarography is an electroanalytical technique that measures the current flowing between two electrodes in the solution (in the presence of gradually increasing applied voltage) to determine the concentration of solute and its nature respectively
Polarography is based upon the principle that gradually increasing voltage is applied between two electrodes, one of which is polarisable (dropping mercury electrode) and other is non-polarisable and current flowing between the two electrodes is recorded.
A sigmoid shape current-voltage curve is obtained from which half wave potential as well as diffusion current is calculated.
Diffusion current is used for determination of concentration of substance.
Half wave potential is characteristic of every element.
Ilkovic equation is a relation used in polarography relating the diffusion current (id) and the concentration of the non-polarisable electrode, i.e., the substance reduced or oxidised at the dropping mercury electrode (polarisable electrode).
Definitions of types of currents
1. Residual current (ir), 2. Migration current (im): , 3. Diffusion current (id) 4.Half wave potential 5. Limiting current (il)
Dropping mercury electrode- Dropping mercury electrode (DME) is a polarisable electrode and can act as both anode and cathode.
The pool of mercury acts as counter electrode,
i.e., anode if DME is cathode or
cathode if DME is anode.
The counter electrode is a non-polarisable electrode.
To the analyte solution, electrolyte like KCl is added i.e., 50-100 times of sample concentration.
Pure nitrogen or hydrogen gas is bubbled through the solution, to expel (remove) out oxygen.
Eg: If the analyte solution contains cadmium ions, then cadmium ions are discharged at cathode (-)
Cd2+ + 2e- → Cd
Then, gradually increasing voltage is applied to the polarographic cell and current is recorded.
Graph is plotted between voltage applied and current. This graph is called Polarograph and the apparatus is known as Polarogram.
The diffusion current produced is directly proportional to concentration of analyte and this is used in quantitative analysis.
The half wave potential is characteristic of every compound and this is used in qualitative analysis.
Graph is plotted between voltage applied and current. This graph is called Polarograph and the apparatus is known as Polarogram.
The diffusion current produced is directly proportional to concentration of analyte and this is used in quantitative analysis.
The half wave potential is characteristic of every compound
Potentiometry is the field of electro-analytical chemistry in which potential is measured without current flow.
It is a method of analysis in which we determine the concentration of solute in solution and the potential difference between two electrodes.
Introduction – cells – types - representation of galvanic cell - electrode potential - Nernst equation (derivation of cell EMF) - calculation of cell EMF from single electrode potential - reference electrode: construction, working and applications of standard hydrogen electrode, standard calomel electrode - glass electrode – EMF series and its applications - potentiometric titrations (redox) - conductometric titrations - mixture of weak and strong acid vs strong base.
Potentiometry: Electrical potential, electrochemical cell, reference electrodes, indicator
electrodes, measurement of potential and Ph, construction and working of electrodes,
Potentiometric titrations, methods of detecting end point, Karl Fischer titration.
Potentiometry, Electrochemical cell, construction and working of indicator an...Vandana Devesh Sharma
Potentiometry - Electrochemical cell -Construction and working of reference (Standard hydrogen, silver chloride electrode and calomel electrode)
Indicator electrodes (metal electrodes and glass electrode)
Methods to determine end point of potentiometric titration
and applications
Potentiometry is the method to find the concentration of solute in
A given solution by measuring the potential between two Electrodes
(reference and Indicator electrode) . Potentiometric titration involves
the measurement of the potential of the indicator electrode and
reference electrode.
In potentiometric titration reference and indicator electrodes are
immersed in the solution of particular analyte (titrand) and
potential of indicator electrode is measured with relation to
reference electrode.
Titrant is added in analyte (Titrand) and change in potential is noted
down.
At the end point there is sharp change in potential on indicator
electrode.
Graph is plotted between the indicator electrode potential and
volume of titrant added.
This method is used for determination of sharp end point.
Types of Potentiometric Titration
1. Acid-base titration 2. Redox Titration 3.Complexometric titration 4. Precipitation Titration
Instructions for Submissions thorugh G- Classroom.pptxJheel Barad
This presentation provides a briefing on how to upload submissions and documents in Google Classroom. It was prepared as part of an orientation for new Sainik School in-service teacher trainees. As a training officer, my goal is to ensure that you are comfortable and proficient with this essential tool for managing assignments and fostering student engagement.
Synthetic Fiber Construction in lab .pptxPavel ( NSTU)
Synthetic fiber production is a fascinating and complex field that blends chemistry, engineering, and environmental science. By understanding these aspects, students can gain a comprehensive view of synthetic fiber production, its impact on society and the environment, and the potential for future innovations. Synthetic fibers play a crucial role in modern society, impacting various aspects of daily life, industry, and the environment. ynthetic fibers are integral to modern life, offering a range of benefits from cost-effectiveness and versatility to innovative applications and performance characteristics. While they pose environmental challenges, ongoing research and development aim to create more sustainable and eco-friendly alternatives. Understanding the importance of synthetic fibers helps in appreciating their role in the economy, industry, and daily life, while also emphasizing the need for sustainable practices and innovation.
How to Create Map Views in the Odoo 17 ERPCeline George
The map views are useful for providing a geographical representation of data. They allow users to visualize and analyze the data in a more intuitive manner.
2024.06.01 Introducing a competency framework for languag learning materials ...Sandy Millin
http://sandymillin.wordpress.com/iateflwebinar2024
Published classroom materials form the basis of syllabuses, drive teacher professional development, and have a potentially huge influence on learners, teachers and education systems. All teachers also create their own materials, whether a few sentences on a blackboard, a highly-structured fully-realised online course, or anything in between. Despite this, the knowledge and skills needed to create effective language learning materials are rarely part of teacher training, and are mostly learnt by trial and error.
Knowledge and skills frameworks, generally called competency frameworks, for ELT teachers, trainers and managers have existed for a few years now. However, until I created one for my MA dissertation, there wasn’t one drawing together what we need to know and do to be able to effectively produce language learning materials.
This webinar will introduce you to my framework, highlighting the key competencies I identified from my research. It will also show how anybody involved in language teaching (any language, not just English!), teacher training, managing schools or developing language learning materials can benefit from using the framework.
Students, digital devices and success - Andreas Schleicher - 27 May 2024..pptxEduSkills OECD
Andreas Schleicher presents at the OECD webinar ‘Digital devices in schools: detrimental distraction or secret to success?’ on 27 May 2024. The presentation was based on findings from PISA 2022 results and the webinar helped launch the PISA in Focus ‘Managing screen time: How to protect and equip students against distraction’ https://www.oecd-ilibrary.org/education/managing-screen-time_7c225af4-en and the OECD Education Policy Perspective ‘Students, digital devices and success’ can be found here - https://oe.cd/il/5yV
This is a presentation by Dada Robert in a Your Skill Boost masterclass organised by the Excellence Foundation for South Sudan (EFSS) on Saturday, the 25th and Sunday, the 26th of May 2024.
He discussed the concept of quality improvement, emphasizing its applicability to various aspects of life, including personal, project, and program improvements. He defined quality as doing the right thing at the right time in the right way to achieve the best possible results and discussed the concept of the "gap" between what we know and what we do, and how this gap represents the areas we need to improve. He explained the scientific approach to quality improvement, which involves systematic performance analysis, testing and learning, and implementing change ideas. He also highlighted the importance of client focus and a team approach to quality improvement.
Palestine last event orientationfvgnh .pptxRaedMohamed3
An EFL lesson about the current events in Palestine. It is intended to be for intermediate students who wish to increase their listening skills through a short lesson in power point.
How to Split Bills in the Odoo 17 POS ModuleCeline George
Bills have a main role in point of sale procedure. It will help to track sales, handling payments and giving receipts to customers. Bill splitting also has an important role in POS. For example, If some friends come together for dinner and if they want to divide the bill then it is possible by POS bill splitting. This slide will show how to split bills in odoo 17 POS.
1. Dr. B. R Ambedkar University
Department of Pharmacy,
Agra-282002
Guidance of Sir. Mr. Vijay Yadav
2. PRINCIPLE
When a metal strip is placed in a solution
of its own ions there are two possibilities
or tendencies:
Metal atoms may dissolve in the solution as
positive ions leaving electrons on the
electrode.
Metal ions may take up electrons from
electrode and get deposited as neutral atoms
In this way A POTENTIAL DIFFERENCE is
setup b/w electrode and solution .
3. POTENTIOMETER
It is instrument used to determine the
potential differences between a reference
electrode and an indicator electrode. These
two electrodes form electro chemical cell that
are dipped in solution to be analyzed.
Measured potential can be used to determine
the quantity of analyte in terms of
concentration.
4.
5. ELECTRODE POTENTIAL
Tendency of electrode to lose or gain electrons
Standard Potential
Potential of pure metal when it is dipped
in 1 Molar solution of its own ions at 25°C
(298K) is known as standard Electrode
potential.
6. Oxidation Potential
The potential of substance to get oxidized is
called oxidation potential.
Reduction Potential
The potential of substance to get reduced is
called reduction potential.
9. WORKING
At its most basic, a potentiometer consists of two
electrodes, whose reduction potentials differ,
inserted in a test solution. The voltmeter is attached
to the electrodes to measure the potential difference
between them.
One of the electrodes is a reference electrode,
whose electrode potential is known.
The other electrode is the test electrode.
The test electrode is usually either a metal
immersed in a solution of its own ions, whose
concentration you wish to discover, or a carbon rod
electrode sitting a solution which contains the ions
of interest in two different oxidation states.
10. 1. Oxidation take place at anode.
For example on zinc electrode
Zn → Zn2+ + 2e-
1. Reduction take place at cathode.
For example on copper electrode
Cu2+ + 2e−→ Cu
When redox reaction take place than potential
is develop which is measured by
galvanometer.
11. Electrode Potential is the potential of
electrochemical cell and can be represented
as :
E cell = E indicator - E reference
+E j
Ej= potential develops across the liquid
junction at each end of salt bridge it is
negligible .
15. SHE
The standard H2 electrode potential is defined as the potential that is
developed between the H2 gas adsorbed on the pt metal and H+ of the
solution when the H2 gas at a pressure of 760 mm of Hg is in
equilibrium with H+ of unit concentration
Working:
Pt foil : coated with black pt
1 molar HCl solution
Pure H2 gas bubbled continuously at 1 atm.
Pt act as conductor, inert and facilitate in
attaining equilibrium
Electrode Potential is 0.00 volts
H2 (gas) ↔ 2H+ (ions) + 2e-
(electrons)
16.
17. Limitations :
1. Can’t be used in solution containing strong
oxidizing agents.
2. Difficult and expensive to maintain.
3. Excess of H2 bubbling out carries little HCl
with it and hence the H+ concentration
decreases. In such a system, it is difficult to
maintain the concentration of HCl at 1M.
18. CALOMEL ELECTRODE
Most commonly used electrode in potentiometry
Tube 5-15cm long, 0.5-1 cm in diameter.
Slurry of mercury & mercurous chloride with
saturated soln of KCl
Connected by a small opening with saturated
solution of KCl.
Pt metal is placed inside the slurry
Ceramic fiber act as salt bridge
2Hg +2Cl¯ → Hg2Cl2 + 2e¯
E = 0.2444 at 25°C
20. Advantages:
Concentration of chloride ions don’t change
even some of the solvent get evaporated.
Generates small junction potential so more
accurate
Limitations :
Mostly saturated solution of KCl is used and
that is temperature dependent.
21. SILVER-SILVER CHLORIDE ELECTRODE
It consist of silver wire coated with AgCl
Coating may be electroplating or Physical.
This coated wire is placed in 1M solution of
AgCl.
Ag + Cl¯ ↔ AgCl + 1e¯
E= 0.199V
Advantages:
Easy handling, and cost effective
Limitation: sometimes show reactivity.
24. METAL INDICATOR
ELECTRODESMetal electrode develops electric potential as a
result of redox reaction at its surface.
1. First Order Electrode
A first order electrode involves the metal in contact
with its own ions, such as Ag, Ag+ or Zn, Zn.
Ag⁺ + e¯ ↔ Ag (s) E= 0.800
Limitation:
metallic indicator electrodes are not very selective
and
respond not only to their own cations but also to other
more easily reduced cations.
– Many metal electrodes can be used only in neutral
or basic solutions because they dissolve in the
presence of acids
25. 2.SECOND ORDER ELECTRODE
A second-order electrode is one that responds to the
presence of precipitating or complexing ions. For
example, silver wire could serve as the indicator
electrode for chloride.
Ag +Cl¯ ↔ AgCl + e¯ E= 0.199
26. 3. INERT ELECTRODE
The most commonly used indicator electrodes
are known as inert. These electrodes are not
involved in the half-cell reactions of the
electrochemical species. Typical inert
electrodes are platinum, gold, and carbon.
Inert electrodes are responsive to any
reversible redox system; these are widely
used in potentiometric work.
27. GLASS MEMBRANE ELECTRODE
Its most commonly used indicator electrode
It involves Ion Exchange reaction
Membrane is made up of chemically bonded
Na2O, SiO2 and Al2O3
The Glass bulb is filled with solution of HCl &
KCl, silver acetate coated with AgCl is
inserted as Electrode.
28.
29.
30. WORKING
First glass absorb water
Then H ions can move in the direction of lesser
concentration and replace Na ions and others in
the glass membrane.
SiO2-Na⁺ + H⁺ → SiO- H⁺ + Na⁺
As a result of diffusion and exchange process a
potential develops on each side of glass membrane
31. APPLICATIONS
Its potential is not effected by the presence of
strong reducing and oxidizing agents.
It operates over a wide pH range,
It respond fast and function well in
physiological systems
Used in pH meter.
32.
33. HYDROGEN ELECTRODE
Used in acid base titration but very limited
application because many organic
substances directly react with hydrogen
gas.
34. QUINHYDRONE ELECTRODE
Contain a solution of Quinones and
Hydroquinones prepared from Quinhydrone
2QH → Q+H2Q
Simple and easily attains equilibrium
employed in the presence of mild oxi and
red agents at pH8
Sensitive to high conc of salts and oxi & red
agents.
35. The electrode consists of an inert metal
electrode (usually a platinum wire) in contact
with quinhydrone crystals and a water-based
solution. Quinhydrone is slightly soluble in
water, dissolving to form a mixture of two
substances, quinone and hydroquinone, with
the two substances present at equal
concentration. Each one of the two substances
can easily be oxidised or reduced to the other.
The potential at the inert electrode depends on
the ratio of the activity of two substances
(quinone-hydroquinone), and also the
hydrogen ion concentration. The electrode half-
reaction is:
Hydroquinone ↔ Quinone + 2H+ +2e-
36. For practical pH measurement, a second pH independent
reference electrode (such as a silver chloride electrode) is
also used. This reference electrode does not respond to
the pH. The difference between the potential of the two
electrodes depends (primarily) on the activity of H+ in the
solution. It is this potential difference which is measured
and converted to a pH value.
The quinhydrone electrode is not reliable above pH 8. It is
also unreliable in the presence of strong oxidising or
reducing agents, which would disturb the equilibrium
between hydroquinone and quinone. It is also subject to
errors in solutions containing proteins or high
concentrations of salts.
Other electrodes commonly used for measuring pH are
the glass electrode, the hydrogen electrode, the antimony
– antimony oxide electrode, and the ion-sensitive field
effect transistor ISFET electrode.
37. SALT BRIDGE
U shaped tube filled with an inert
electrolyte
1. Glass tube bridge (gel+ KI or Na2SO4)
2. Filter tube bridge (filter paper+KCl or NaCl)
Function:
1. Allow electrical contact b/w 2 solutions.
2. Prevent mixing of two solutions.
3. Maintain electrical neutrality.
38.
39. TITRATION :
Quantitative measuring procedure in which a
liquid solution is added to a mixture until
some distinctive feature, signal or end point
is observed.
40. POTENTIOMETRIC TITRATION
It’s a volumetric method in which potential
between two electrodes (reference &
indicator) is measured as a function of added
reagent volume.
44. PRECIPITATION TITRATION
Volumetric methods based upon the
formation of slightly soluble precipitate are
called " precipitation titration " .
Because of the precipitating titration based
upon utilizing silver nitrate
(AgNO3) as a precipitating agent, then
it called " argentimetric
processes " .
Precipitation titration is a very important ,
because it is a perfect method
for determine halogens and some metal
ions
45. COMPLEX FORMATION TITRATION
Complex ions ( coordination compounds) are
produce from reaction of
many metal ions (electrons accepter) with
electron pair donors .
The donor species (or called ligands) must
have at least one pair of
unshared electrons for bond formation
46. NEUTRALIZATION TITRATION
Neutralization titrations are performed
with standard solutions of strong acids
or
bases. While a single solution (of either
acid or base) is sufficient for the titration
of
a given type of analyte, it is convenient
to have standard solutions of both acid
and
base available in case back-titration is
needed to locate the end point more
47. OXIDATION-REDUCTION TITRATION
A redox titration is a type of titration based on a
redox reaction between the analyte and titrant.
Redox titration may involve the use of a redox
indicator and/or a potentiometer. Common
examples of a redox titration is treating a
solution of iodine with a reducing agent and
using starch as an indicator. Iodine forms an
intensely blue complex with starch. Iodine (I2)
can be reduced to iodide(I−) by
e.g. thiosulphate (S2O3
2−), and when all iodine is
spent the blue colour disappears. This is called
an iodometric titration
48. APPLICATIONS OF POTENTIOMETRY
Analysis of pollutants in water
Drug Analysis in Pharmaceutical industry
Food industry for analysis of quality
Biochemical and biological Assay or analysis
To check the quality of cosmetics
Also used as analytical tool in Textile, paper,
paints, explosive energy and more .